DESCRIPTION The overall goal of this proposal is to further the understanding of interhemispheric modulation of somatosensory receptive fields after unilateral ablation of the hand region in anterior parietal cortex (APC). Although there are few direct connections between APC in the two hemispheres, preliminary data show a large increase in the size of receptive fields in the hand area of the side contralateral to the injury. This highly plastic aspect of recovery from injury has not been noted previously, and may provide insight into mechanisms involved in recovery. In the proposed experiments, areas 3b, 3a, and adjacent 1 and 2 of APC will be surgically ablated in anesthetized macaques. An acute and eight- week recovery period will be used, in order to assess early and late alterations. After recovery, chronic recording procedures will be applied to assess the extent of receptive fields in the hand region of APC, secondary somatosensory cortex (SII) and thalamus of the side contralateral to the injury. These areas will be examined with immunocytochemistry for neurotransmitters and receptors, the phosphorylated form of microtubule associated protein 1B, and growth associated phosphoprotein 43 in order to gain information on possible contributions to interhemispheric transfer of information and reorganization after injury.